Conventional optical sensors utilize spherical domes and flat windows in order to facilitate optical design, aberration correction, enhanced imaging quality, hardware fabrication and interferometric acceptance testing. As used herein, the term "conformal" optics describe optical systems that are designed with the operational environment as the primary consideration and the optical imaging properties as a secondary concern. As a result, conformal domes and windows for missile and airborne fire control systems are driven by aerodynamic performance issues, e.g. decreased aerodynamic drag, increased missile velocity and extended operational range, and result in highly aspheric dome geometries that are more elongated in shape.
A major disadvantage of these highly aspheric surfaces is the large aberrations they produce in the transmitted optical wavefront. In addition, the inherent asymmetry of conformal surfaces leads to variations in the aberration content presented to the optical sensor as it is gimballed across the field of regard. These two factors degrade the sensor's ability to properly image targets of interest and hence undermine the overall system performance. Consequently, the aerodynamic advantages of conformal domes and windows cannot be realized in practical systems unless dynamic aberration correction techniques are developed to restore adequate optical imaging capabilities. As a result, no known operational missile system currently employs a conformal dome in combination with an optical sensor system.
It is acknowledged that the use of cylindrical elements for astigmatic correction is commonplace in the optical industry. It is also acknowledged that the separation between optical elements is a powerful variable for achieving desired optical performance. However, no prior art applies dynamic axial translation of cylindrical elements to correct varying aberrations resulting from conformal/aspheric domes and windows in missile and airborne fire control applications.
It would therefore represent an advance in the art to provide a technique for optically compensating the variable aberrations introduced by conformal domes/windows.